Subsurface blowout prevention

ABSTRACT

In a tool and method for automatic subsurface closure of a well to prevent blowout conditions, the tool including a movable sealing means and a fluid-flow control means positioned above the sealing means, the movable sealing means being adapted to shut in the well in response to a subsurface pressure condition, the fluid flow control means automatically providing an opening for circulating drilling fluid above the sealed off area, the improvement comprising: an elongated mandrel adapted to allow the movement of the drill string after the sealing means effectively shuts in the well, a pressure sampling valve to monitor the external pressure of the fluid below the activated sealing means, and a mechanical release mechanism adapted to operate the fluid flow control means thereby mechanically contracting the sealing means.

United States Mott [75] Inventor: James D. Mott, Houston, Tex.

[73] Assignee: Michael P. Breston, Houston, Tex.

a part interest [22] Filed: Oct. 16, 1970 [21] Appl. No.: 81,327

[52] 11.8. CI 166/315, 166/184, 166/187, 175/325 [51] Int. Cl E211) 23/00, E21b 33/12 [58] Field of Search 166/184, 120, 187, 166/196, 237, 240, 315, 179; 175/320, 325

[56] References Cited UNITED STATES PATENTS 2,606,618 8/1952 Page 166/179 3,339,637 9/1967 Holden.... 166/120 2,229,493 l/l941 Croft et al. 166/196 2,942,667 l/1960 Blood et al. 175/325 3,180,419 4/1965 Cochran et a1. 166/120 3,181,614 5/1965 Brown 166/122 3,225,844 12/1965 Roberts 175/325 3,235,017 2/1966 Lynes 166/196 3,334,691 8/1967 Parker.. 175/325 3,370,657 2/1968 Antle 175/325 I: p {f A n I i l A, A

I i ll 1 SUBSURFACE BLOWOUT PREVENTION i1 3;7-46,097 1 ,4 51 July 17,1973

3,427,651 2/1969 Bielstein et al. 166/187 3,503,461 3/1970 Shirley 166/187 3,529,665 9/1970 Malone 166/187 Primary ExaminerJames A. Leppink AttorneyMichael P. Breston and Alfred B. Levine In a tool and method for automatic subsurface closure ofa well to prevent blowout conditions, the tool including a movable sealing means and a fluid-flow control means positioned above the sealing means, the movable sealing means being adapted to shut in the well in response to a subsurface pressure condition, the fluid flow control means automatically providing an opening for circulating drilling fluid above the sealed off area, the improvement comprising: an elongated mandrel adapted to allow the movement of the drill string after the sealing means effectively shuts in the well, a pressure sampling valve to monitor the external pressure of the fluid below the activated sealing means, and a mechanical release mechanism adapted to operate the fluid flow control means thereby mechanically contracting the sealing means.

ABSTRACT 41 Claims, 7 Drawing Figures SUBSURFACE BLOWOUT PREVENTION BACKGROUND OF THE INVENTION In my copending patent application, Ser. No. 12,823, for Automatic Surface Blowout Prevention, there is disclosed an automatic tool (herein called the former tool) for shutting in a well when a subsurface formation pressure becomes excessive, thereby preventing a blowout condition from arising. The former tool includes a fluid-inflatable packer, and a fluid-circulating valve positioned above the packer. After the packer extends and makes a seal with the wall of the borehole, the circulating valve automatically opens to allow fluid circulation to take place between the inside and outside of the drill string. Weight is added to the drilling fluid and when its pressure above the expanded packer exceeds the pressure below the packer, the packer actuating mechanism will cause the packer to contract. Thereafter, normal drilling operations can resume.

Under some drilling operations, it may be desired to prevent the drill string from sticking to the wall of the borehole when the packer is expanded and in fixed engagement with the wall of the borehole.

It may also be desired, when the packer is expanded and in fixed engagement with the wall of the formation, to monitor the external pressure of the fluid below the expanded packer.

Another desired feature is to be able to mechanically close the circulating valve so that the packer can be caused to contract.

Accordingly, it is a general object of the present invention to add to the former tool the above-described and other desired features.

SUMMARY OF THE INVENTION To the former tool are added means to allow for the reciprocation and rotation of the drill string while the packer is in its expanded and formation-engaging position, a mechanism to monitor the fluid pressure existing in the borehole below the expanded packer, and a mechanical, packer-release mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified view, partly in section, of the former tool;

FIGS. 2A and 2B show a simplified view, similar to FIG. 1, of the present tool;

FIGS. 3A, 3B and 3C are detail views, partly in section, of a preferred embodiment of the present tool with the movable parts shown in their activated positions; and

FIG. 4 is a view on line 4-4 in FIG. 3B.

BRIEF DESCRIPTION OF FORMER TOOL FIG. I shows in simplified form the former tool 10 described in said copending patent application. To facilitate the description of the present tool, the same reference characters, as used in the drawings of said copending patent application, will be employed herein to designate those parts which are common to both the former tool and the present tool.

Normally tool 10 forms part of and is positioned at a selected, desired elevation along a drill string assembly, generally designated as 11. String 11 includes drill pipe 12, a top connector 23, collars l4 and a drill bit 16. String 11 extends into a borehole 13 which traverses a formation 18. Borehole 13 has a wall 19.

To carry out drilling operations, a drilling fluid is pumped from the surface of the well down string 11, through restricted orifices in drill bit 16, and up through an annular area of annulus 20 between the outer wall of string 11 and wall 19 of borehole 13. After circulation of the drilling fluid is established, for the same vertical elevation, the hydraulic pressure inside strings 11 is greater than the pressure outside string 11 within annulus 20.

As bit 16 continues to drill, a formation may be encountered whose pressure is greater than the pressure of the circulation fluid in the adjacent annulus 20. This condition may cause the well to blow out unless preventive measures are immediately taken, preferably automatically without the intervention of human efforts. A check valve 21, positioned at the lower end of tool 10, will prevent the formations pressure from fluidly communicating with the interior of drill string 11.

Generally, former tool 10 includes a mandrel 34 having inner and outer walls 24, 25. Mandrel 34 has ports 68, 150, 128 and extends throughout the entire length of tool 10. Mounted on wall 25 are: a fluid-circulating, normally closed valve 26, and a fluid-inflatable packer 28 which also includes a packer-setting mechanism 30, When circulating valve 26 opens, a chamber 126 is constantly in fluid communication through openings 128 with the fluid pressure inside mandrel 34. When valve 26 opens, the pressure inside mandrel 34 and in chamber 126 communicates through port 130 with the pressure in the annulus 20.

BRIEF DESCRIPTION OF THE OPERATION OF TOOL 10 As drill string 11 is being lowered into annulus 20, tool 10 is in its locked condition. Check valve 21 then prevents the drilling fluid in annulus 20 from entering the inside of drill string 11. Thereafter, drilling fluid is circulated down through drill string 11, bit 16, and up through the annular area 20. The packer-setting mechanism 30 is in its deactivated or contracted condition.

When drill bit 16 encounters a high-pressure formation which may be sufficient to cause a blowout condition, the forrnations fluid pressure will communicate through a port 71 with a chamber 70. Check valve 21 will prevent the formation's pressure from lifting the drilling fluid inside drill string 11. The packer-setting mechanism 30 will become activated to cause the packer 28 to inflate and expand radially.

For valve 26 to open, the pressure outside tool 10 and above packer 28 must be less than the pressure outside tool 10 and below packer 28. This condition is met only when (1) packer 28 has sealingly engaged wall 19, and (2) the outside pressure below packer 28 is greater than the outside pressure above packer 28. When valve 26 opens, fluid communication is established between the valves internal and external ports 128, 130, that is, between the inside and outside of drill string 11 above the sealed off area.

After valve 26 opens, the circulation of drilling fluid can be established through valve 26. The weight of the drilling fluid is increased so that the internal pressure inside mandrel 34 becomes again greater than the external pressure outside mandrel 34 and below packer 28. When this internal pressure becomes greater than the external pressure, the packer-setting mechanism 30 will return to its normally deactivated condition, packer 28 will contract, and circulating valve.26 will close. When circulating valve 26 closes, fluid communication stops between its ports 128, 130. Tool has now completed a full operating cycle: packer 28 was activated and reversibly deactivated, and valve 26 opened and closed.

BRIEF DESCRIPTION OF PRESENT TOOL 199 The improved tool of this invention, shown in FIG. 2, is generally designated as 199. Tool 199 is obtained by adding to former tool 10 the following features: Mandrel 200 To prevent drill string 11 from sticking to wall 19 of borehole 13 below expanded packer 28, it may be desired to move drill string 11 up and down (reciprocate) and/or to rotate drill string 11 while packer 28 is in its expanded state and in fixed engagement with wall 19. The movement (which includes reciprocation and/or rotation) of drill string 11 can be accomplished by using an elongated inner mandrel 200 which extends throughout the entire length of former tool 10. Mandrel 200 is considerably longer than tool 10 to allow substantial up and down travel of mandrel 200 relative to stationary tool 10. Ports 201 in the wall on mandrel 200 allow, under certain operating conditions, fluid communication with ports 128, 150 and 68 in mandrel 34 and with port 130 in circulating valve 26. Tool 10 is provided with end seals 232, 244 which allow a sealing engagement between former tool 10 and the outer cylindrical wall of mandrel 200. When mandrel 200 moves relative to tool 10, ports 201 remain between seals 232, 244.

Releasable Securing Device 249 A releasable securing device 249 releasably couples tool 10 to the outer cylindrical wall of mandrel 200. Tool 10 is continuously attached to mandrel 200 except when the packer-setting mechanism 30 becomes activated. The packer-setting mechanism 30 releases securing device 249, thereby detaching tool 10 from the outer wall of mandrel 200.

Mandrel 200 can move (reciprocate and/or rotate) relative to tool 10, that is, relative to mandrel 34, while packer 28 is expanded and in fixed engagement with wall 19 of borehole 13. This movement will assist in preventing string 11 from sticking to wall 19 of borehole 13.

Pressure Sampling Valve 204 It may also be desired, when packer 28 is expanded and in fixed engagement with wall 19, to monitor the external pressure of the fluid below packer 28. This can be accomplished with a pressure-sampling valve 204 having internal and external ports 280, 278. Under all operating conditions valve 204 is closed. Fluid communication between ports 278, 280 is established only when (l) packer 28 engages wall 19, and (2) when an upward pull is exerted on drill string 11.

When valve 204 is open, ports 201 are closed, and

,, the external fluid pressure below packer 28 will communicate with the internal pressure of mandrel 200. The pressure inside mandrel 200 can be measured at the surface of the well in a conventional manner. After the pressure is monitored at the surface, the lowering of drill string 11 will allow valve 204 to close automatically. Mechanical Release of Packer 28 It may also be desired to mechanically close circulating valve 26 so that packer 28 can be caused to contract. This is accomplished by lowering drill string l1 so that the top connector 23 will mechanically engage and close circulating valve 26. By increasing the pressure of the circulating fluid through drill string 11, packer 28 will move from its expanded to its contracted state.

COMPLETE DESCRIPTION OF PRESENT TOOL 199 (FIGS. 2, 3 AND 4) The Packer Setting Mechanism 30 Guide pins 36 of mechanism 30 extend into spaced, longitudinal slots 38 to allow for the up and down movement of mechanism 30. A cylinder 42 is threadedly connected to a packer piston 44. Cylinder 42 is releasably secured by a snap ring 46 and a fixed, splined, retainer ring 48. Ring 48 defines several (six) openings 50. Through each opening 50 vertically extends a finger 52 of a movable expander ring 54. The tip 56 of each finger 52 is in contact with a power piston 58 which is slidably mounted between wall 25 and the cylindrical inner wall 60 of cylinder 42. Piston 58 can be moved between the upper surface 49 of the retainer ring 48 and a shoulder 64 of cylinder 42. Between the internal wall 60 of cylinder 42 and the external wall 25 of mandrel 34 is formed a long chamber 66 which fluidly communicates with a chamber 208 through a port 68. Chamber 208 is between mandrel 200 and mandrel 34.

Below piston 58 is a chamber 70 which fluidly communicates with the pressure in the annular area 20 through ports 71. Above piston 58 is a chamber 66. A sleeve is fixedly secured on wall 25 by rings 82, 84. Wall 60 of cylinder 42 slides on a seal 86 in the outer wall of sleeve 80. A port 88 communicates the pressure between a chamber 90 and the pressure in annulus 20. The annulus pressure is exerted on the lower surface 92 of the packer piston 44. The outer cylindrical portion 94 of cylinder 44 defines the previously mentioned, vertically extending, spaced slots 38. The top surface 96 of packer piston 44 is exposed to the pressure of an enclosed fluid in packer chamber 98. The packer fluid is typically a heavy oil having a low vapor pressure. The Packer 28 Chamber 98 is formed between the outer wall 25 of mandrel 34 and the inner wall 100 of a cylinder 102. Pins 36 of cylinder 102 extend into slots 38. Cylinder 102 forms integral part with a movable flexible member, or fluid-expandable packer wall 104. Wall 104, in turn, forms integral part with a sleeve 106 which is threadedly connected to a sleeve 108. Sleeve 108 defines a stop shoulder 110 for arresting the further movement of the bottom surface 112 of a piston 114. A fluid passageway 116 establishes fluid communication between chambers 98 and 118.

The Circulating Valve 26 A valve cylinder 120 is threadedly connected on one hand to piston 114 and on the other hand to a valveoperating sleeve 207. A shoulder 122 on cylinder 120, when cylinder 120 is in its elevated position, will abuttingly engage the bottom surface 124 of a packing retainer sleeve 202. A chamber 126 is in constant fluid communication through openings 128 with chamber 208. When the circulating valve 26 is open, chamber 126 is in fluid communication through ports 130 with the fluid pressure in the annulus 20. A cylinder 132 is fixedly mounted on the outer wall 25 by two retaining rings 134, 136. Cylinder 132 defines an inclined valve surface 138 which snuggly engages surface 140 of cylinder 120. A seal 139 is provided on surface 138. A floating piston 142 defines a shoulder 144 for engaging a coiled spring 146 which also rests on the top surface 148 of piston 114. Chamber 152 is in fluid communication through ports 150 with chamber 208.

Operating Valve 206 A packing retainer ring 210 defines a plurality of openings 212 to allow fluid communication through ports 214 between chamber 208 and a chamber 216. Chamber 216 is in fluid communication with a chamber 218 through ports 220, 222 in the packing-retainer sleeve 202 and a packing-separator sleeve 224, respectively. Chamber 218 fluidly communicates through ports 261 with the inside of mandrel 2ll0when ports 201 of mandrel 266 lie between seals 232, 234. O-rings 226, 228 render chamber 216 fluid tight. When O-ring 228 moves upwardly, ports 214 in the packing retainer sleeve 202 will be blocked by O-ring 228 and another O-ring 230. Between packing-retainer ring 210 and packing-separator sleeve 224 is the packing seal 234. Between the upper end of sleeve 224 and sleeve 202 is the other packing seal 232. Packing seal 232 prevents fluid passage between chamber 218 and annulus 20, and packing seal 234 prevents fluid passage between chambers 2118, 218. Bearing rings 236, 238 prevent wear when mandrel 260 is moved relative to mandrel 34.

A top surface 239 on sleeve 207 receives the bottom shoulder 240 of top connector 23. Connector 23 threadedly secures mandrel 200 to the lowermost drill pipe 12. A packing seal 244 is retained by a retainer ring 242 below the bottom end of mandrel 34. A latch member 246 is provided with a spring-biased locking device 248 for securing mandrel 200 to mandrel 34. A wedge 2S0 maintains the locking device 248 in engagement with mandrel 200 when sleeve 42 is in its lowermost position. Thus, parts 246, 248 and 250 form a releasable securing device, generally designated as 249. Pressure Sampling Valve 204 Mounted on the outer wall of mandrel 200 is a piston 262 secured by retainer rings 254, 256. A sliding piston 258 defines a chamber 260 in fluid communication through a port 262 with the inside of mandrel 2611. A valve body 264 is threadedly secured to a retainer sleeve 266 and to a spring retainer 268. A plurality of coil springs 2711, disposed between spring holders 272, 274, maintain the valve body 264 in its elevated position. A retainer ring 276 attaches spring holder 272 to mandrel 206. The bottom end of mandrel 260 is threadedly secured to a bottom coupling device 22. A check valve 21 below coupling device 22will prevent the fluid pressure in annulus 20 from fluidly communieating with the interior of mandrel 2011.

Operation of Tool 199 in operation, tool 199 is connected to a drill collar 14 and to a drill pipe 12 by connectors 22, 23, respectively. As drill string 11 is being lowered into the annular area 20, tool 199 remains in its deactivated and locked condition. Check valve 21 prevents the drilling fluid which is in borehole 13 from entering into mandrel 260. Accordingly, before fluid circulation begins, the exterior hydrostatic pressure is greater than the pressure inside mandrel 200, and an upward force becomes exerted on the power piston 58. The movement of piston 58 is arrested by shoulder 64 of cylinder 42. Snap ring 46 locks cylinder 42 to mandrel 34.

Thereafter, in conventional manner, drill string 11 is filled with fluid and circulation is established through mandrel 200, bit 16, and up through the annulus 20. The interior pressure inside mandrel 200 then becomes greater than the exterior pressure in annulus 20.

A downwardly directed force now becomes exerted on power piston 58 which pushes against the tips 56 of fingers 52 thereby causing ring 54 to move downwardly against the upper surface 49 of retainer ring 48. Snap ring 46 reduces its diameter to free cylinder 42 for upward movement. The packer-setting mechanism 30 is now in its deactivated and unlocked condition. Cylinder 42 does not move upward, since piston 58 now exerts a downward force against the upper surface 49 of retainer ring 48.

Operation of Packer-Setting Mechanism 30 When drill bit 16 encounters a high-pressure formation 18 sufficient to cause a blowout condition, the formations fluid pressure will communicate through ports 71 with chamber 70. Check valve 21 will prevent the formation s pressure from lifting the drilling fluid inside mandrel 200. Power piston 58 will then move upwardly. An upward force also then becomes exerted on the lower surface 92 of packer piston 44. Since piston 58 pushes cylinder 42 upwardly and an upward force is also exerted on packer piston 44, packer 28 will now become inflated.

Operation of Packer 28 As packer piston 44 moves up into chamber 98, the constant volume fluid in chamber 98 moves up through passageways 116 and causes the flexible wall 104 to move radially outwardly. If possible, a seal will be established between packer wall 104 and wall 19 of bore hole 13. If packer wall 104 does not effectuate a seal, cylinder will not move up, and'circulating valve 26 will remain closed. Conversely, if a wall 19 is encountered and a seal is established therewith, valve 26 can open.

Operation of Circulating Valve 26 Surface 112 of piston 114 is exposed to the pressure inside chambers 98, 118. When the pressure outside tool 199 is greater than the pressure inside mandrel 200, a balanced condition around valve 26 exists and valve 26 is closed. Conversely, when the pressure inside mandrel 260 is greater than the pressure outside tool 199, valve 26 also remains closed. Thus for all conditions, valve 26 will be closed, except when the external pressure below seal 28 is greater than the external pressure above seal 28. This exception is met only when packer 28 has sealingly engaged wall 19 of borehole 13, and a differential pressure is established across packer 28 (with the upper pressure being less than the bottom pressure).

Under normal drilling operations when the pressure inside mandrel 260 is greater than the pressure outside tool 199, the floating piston 142 is at its upper position and engages stop ring 136. Cylinder 120 is forced downwardly and its shoulder tightly engages seal 139 to prevent fluid from communicating between ports 128, 1311.

Upon the occurrence of a blowout condition, the ex ternal fluid pressure below seal 28 becomes greater than the pressure inside mandrel 200 and an upward force is exerted on cylinder 42 and, hence, on packer piston 44, as previously described. The packers fluid in chamber 98 becomes compressed and its wall 104 inflated.

For valve 26 to open, either the outside pressure below packer 28 must increase, or the pressure above packer 28 must decrease. The pressure below packer 28 may become greater than the pressure above packer 28 only when an effective seal is established between wall 104 of packer 28 and wall 19 of borehole 13. It may be possible from the surface to decrease the pressure above the packer 28.

In any event, when the pressure outside tool 199 and above packer 28 is greater than the pressure inside mandrel 200, floating piston 142 will move downwardly, thereby compressing spring 146 and pushing against surface 148 of piston 114. A downward force is thus exerted on cylinder 120. Valve 26 will remain effectively closed and will not accidentally open.

In sum, under all conditions the packer fluid in chamber 98 fluidly communicates with chamber 118 through passageways 116. When pressure conditions in and around tool 199 are such that the outside pressure above packer 28 is less than the outside pressure below packer 28, valve 26 will open.

To open valve 26, piston 114 and cylinder 120 must move upwardly until surface 122 is stopped by surface 124. Fluid communication is now established between ports 128, 130, that is, between chamber 208 and annulus 20 above the sealed off area. Moving with piston 114 is piston 142 thereby carrying upwardly compressed spring 146.

When cylinder 120 moved upwardly, seal 228 also moved upwardly thereby sealing off port 214 from port 220 and breaking fluid communication between chambers 208 and 218. To establish drilling fluid circulation between the inside and outside of tool 199, above packer 28, mandrel 200 must be lowered until ports 201 are below packing seal 234. Fluid circulation will then take place between the inside of mandrel 200, ports 201, chamber 208, port 128, chamber 126 and port 130. The weight of the fluid can be increased so that the internal pressure inside mandrel 200 is again greater than the external pressure below the packer 28.

Thereafter, a downwardly directed force is exerted on piston 58 through port 68. The fluid pressure in chambers 98, 118 is reduced and wall 104 is deflated. Valve 26 closes thereby breaking fluid communication between its ports 128, 130.

It should be now apparent that if the fluid pressure below packer 28 should become excessive, it may not be desired to increase the weight of the circulating fluid to close valve 26. If the weight of the circulating fluid is increased above a predetermined level, the pressure of the circulating fluid may overcome the pressure of one or more zones in formation 18 and break down the formation. To prevent that from happening, it is desired to determine the exact value of the fluid pressure below packer 28 in annulus 20.

Operation of Sampling Valve 204 With valve 26 open, by pulling on the drill string 11, mandrel 200 is raised until ports 201 are positioned between packing seals 232 and 234. Ports 201 are then blocked effectively and are only in communication with sealed off chamber 218.

As the pull on mandrel 200 continues, the upper surface of sleeve 266 encounters the lower surface of sleeve 246, thereby arresting the movement of sleeve 264. Piston 252 continues to move with mandrel 200, thereby opening fluid communication between ports 278 and 280 in members 264, 200, respectively.

By establishing fluid communication between ports 278, 280 the pressure below packer 28 is now transmitted to the pressure inside the mandrel 200 which can be measured at the surface by a suitable instrument.

When the driller determines from the above measurement that the pressure below the packer 28 is not too excessive, he will then establish fluid circulation through circulating valve 26 and increase the weight of the circulating fluid. This is accomplished by lowering drill string 11 (hence lowering mandrel 200), allowing pressure sampling valve 204 to close, and thereby breaking fluid communication between ports 278, 280. The driller continues to lower mandrel 200 until ports 201 are disposed below packing seal 234. In this condition, fluid circulation takes place from the inside of mandrel 200 to the outside of tool 199 through ports 201, chamber 208, ports 128, chamber 126 and ports 130.

On the other hand, if the driller determines from the measurement that the fluid pressure below packer 28 is excessive, then he will lift up string 11 a distance necessary to close fluid communication between ports 201 and chamber 208, but not a sufficient distance to open the pressure-sampling valve 204. Cement may then be pumped down drill string 11 through check valve 21, collar 14, bit 16 and into the formation 18 to thereby seal off the formation.

When packer 28 is in its expanded position, it may be desired to release the packer without increasing the weight of the circulating fluid. This can be accomplished by lowering the drill string 11 until surface 240 of top connector 23 engages surface 239 of operating sleeve 207, thereby forcing sleeve downwardly and closing circulating valve 26. When valve 26 is closed, ports 201 are at their lowermost travel position and are in direct fluid communication with chamber 208 and hence with chamber 66 through ports 68. If the pressure of the circulating fluid is increased sufficiently, power piston 58 will move downwardly thereby unseating packer 28.

It will be appreciated that while a preferred embodiment of this invention has been described in great detail and with reference to certain illustrative values, the invention is not limited thereto and modifications will readily suggest themselves to those skilled in the art, and all such modifications are intended to fall within the scope of the following claims.

What is claimed is:

1. An elongated tool connectable to a string of liquid conducting hollow members for insertion into a wellbore, said tool comprising:

a hollow outer mandrel;

inflatable sealing means mounted on said outer mandrel;

pressure control means mounted on said outer mandrel below said sealing means and being operatively coupled to said sealing means;

said pressure control means a. having means for inflating said sealing means when the outside ambient pressure outside the tool in the wellbore becomes greater than the inside ambient pressure inside the inner bore of the tool,

b. having means for deflating said sealing means when said outside ambient pressure below said sealing means becomes less than said inside ambient pressure, and

c. being operable solely in response to changes in the pressure difference between said outside and inside pressures;

a hollow inner mandrel extending through said outer mandrel, said inner mandrel being connectable between said hollow members,

each end of said outer mandrel being sealingly and slidably mounted on said inner mandrel to allow said inner mandrel to be movable relative to said outer mandrel, and

said inner mandrel defining an upper port for establishing fluid communication between the inner bore of said inner mandrel and the inner bore of said outer mandrel.

2. The tool of claim 1 including,

disabling means coupled to said pressure control means to disable said control means when said tool is initially inserted into said wellbore, and

said disabling means changing to enabling means when said inside ambient pressure becomes greater than said outside ambient pressure.

3. The tool of claim 1 including, normally closed, first fluid communication means mounted on said outer mandrel above said sealing means, and

said communication means open to establish fluid communication between the inside and outside of said tool above said sealing means after said sealing means have effectively sealed off the wellbore around said tool, and the pressure below said sealing means becomes greater than the pressure above said sealing means, and said insideambient pressure remains less than said outside ambient pressure below said sealing means.

4. The tool of claim 3 including,

second fluid communication means in said outer mandrel for maintaining fluid communication between said inner mandrel and said pressure control means.

5. The tool of claim 4 wherein said first fluid communication means is closed when said second communication means is and vice versa.

6. The tool of claim 5 wherein said second fluid communication means is open when said sealing means is inflated thereby allowing an increase in the pressure inside said inner mandrel to operate on said control means to thereby deflate said sealing means.

7. The tool of claim 6 wherein said upper port is in fluid communication with said second communication means when said inner mandrel is moved to an elevated position relative to said outer mandrel.

8. The tool of claim 7 wherein said upper port is in direct fluid communication with said first communication means when said inner mandrel is positioned below said elevated position by a first predetermined distance.

9. The tool of claim 5 wherein said first communication means includes a circulating valve having a body portion coupled to said sealing means.

10. The tool of claim 9 wherein said second fluid communicationmeans includes an operating valve having a body portion coupled to the body portion of said circulating valve to allow the body portions of said circulating and operating valves to move in unison.

11. The tool of claim 10 wherein said second fluid communication means defines an elongated second chamber between said inner and outer mandrels for conducting fluid from said inner mandrel through said upper port and said second communication means to said first sensing element.

12. The tool of claim 11 wherein said second chamber fluidly communicates with said first fluid communication means to allow fluid circulation between the inside and outside of said tool subsequent to the establishment of an effective seal by said 'sealing means against the wall of said wall bore.

13. The tool of claim 12 including intermediate seal means between said inner and outer mandrels adapted to seal off said upper port from said second chamber dependent upon the relative longitudinal positions of said mandrels.

14. The tool of claim 13 wherein said seal means include a top end seal and a bottom end sealto seal off said second chamber.

15. The tool of claim 9 wherein the first communication means includes a second differential-pressure sensing element movably mounted on said outer mandrel, and

said second sensing element assisting in maintaining said circulating valve closed when the pressure inside said inner mandrel is greater than the ambient outside pressure above said sealing means. 16. The tool of claim 15 wherein said second sensing element is a piston movably mounted on said outer mandrel.

17. The tool of claim 1 including, releasable securing means for coupling said inner mandrel to said outer mandrel, said securing means being released by said pressure difference, and

said inner mandrel being longitudinally movable relative to said outer mandrel only after said sealing means, in use, seals off said wellbore.

18. The tool of claim 17 including,

normally closed third fluid communication means mounted on said inner mandrel below said sealing means for establishing fluid communication between said inner mandrel and said borehole and, said third communication means opening upon the upward movement of said inner mandrel relative to said outer mandrel by a second predetermined longitudinal distance.

19. The tool of claim 18 wherein the movement of said inner mandrel relative to said outer mandrel by an amount less than said second predetermined distance allows said third communication means to remain closed, said second communication means to remain closed, said first communication means to remain open, said upper port to be in direct communication with said second communication means, and said second communication means to be sealed off from'said first communication means whereby a. suitable substance can be circulated downwardly through said inner mandrel to shut in said wellbore.

20. The tool of claim 18 wherein said third communication means includes a pressure-sampling valve having a body portion fixedly secured to said inner mandrel, and

said inner mandrel defines a bottom port for maintaining direct fluid communication with said third communication means.

21. The tool of claim 20 wherein said third communication means includes a third differential-pressure sensing element,

said third sensing element assisting in maintaining said pressure sampling valve closed when the pressure inside said inner mandrel is greater than the ambient outside pressure below said sealing means, and said inner mandrel defines an intermediate port fluidly communicating with said third sensing element. 22. The tool of claim 21 wherein said third communication means include a spring for biasing said third sensing element in a direction to assist in maintaining control means to be isolated thereby to prevent the deflating of said sealing means.

24. The tool of claim 23 wherein said operating means is a top connector for connecting said inner mandrel to a top hollow member.

25. The tool of claim 1 wherein said sealing means define a first chamber;

a liquid filling said chamber; and

said control means controlling the pressure of the liquid in said first chamber.

26. The tool of claim 25 wherein said control means include:

a first differential-pressure sensing element responsive to said pressure difference, and

a mechanism controlled by said first sensing element.

27. The tool of claim 25 wherein said sealing means includes an inflatable element adapted to seal off said wellbore when said first chamber becomes pressurized.

28. The tool of claim 26 wherein said first sensing element is a piston mounted on said outer mandrel for longitudinal movement.

29. The tool of claim 28 wherein said mechanism includes a piston adapted to move in said first chamber.

30. The tool of claim 28 including,

locking means for initially securing said mechanism to said outer mandrel, and

said locking means releasing said mechanism when the pressure inside said inner mandrel becomes greater than the outside ambient pressure.

31. The tool of claim 30 wherein the movement of said first sensing element exerts a downward force against said locking means to release said locking means.

32. The tool of claim 31 wherein said inner mandrel, subsequent to the release of said locking means and the establishment of an effective seal in said wellbore by said sealing means, is free to reciprocate and rotate relative to said outer mandrel.

33. The tool of claim 32 including a check valve positioned near the bottom end of said inner mandrel to prevent fluid from the wellbore from entering into said inner mandrel.

34. A hollow well tool connectable to a string of hollow members for circulating fluid between said string and an opening, said tool comprising:

a packer which, in normal use, is contracted to allow unrestricted fluid circulation between said string and said opening, said packer being susceptible of radial expansion to seal off said opening, said packer having a resilient member with an outer surface which, in use, engages the wall of said opening and forms a sealing surface therewith, pressure responsive control means coupled to said packer, said control means, in normal use, being deactivated and becoming activated when the outside ambient pressure becomes relatively high,

said control means, when activated, enabling said packer to radially expand,

an outer hollow mandrel operatively supporting said packer and said pressure responsive means, and

a hollow inner mandrel carrying said outer mandrel,

said inner mandrel, in use, being connectable between said tubular members and being susceptible of longitudinal movement or rotation relative to said outer mandrel.

35. A method for controlling a well having a borehole filled with a fluid including:

lowering a string of hollow members into said borehole, one of said hollow members comprising a detachable and expandable sealing means; continuously monitoring the outside ambient pressure outside said sealing means relative to the inside pressure inside said string;

using a predetermined value of the pressure difference between the outside and inside pressures to cause said sealing means to radially expand;

detaching said sealing means from said one hollow member; and

moving said string relative to said sealing means.

36. The method of claim 35 and,

using another value of said pressure difference to cause said sealing means to contract.

37. The method of claim 36 and,

reciprocating said string relative to said sealing means.

38. The method of claim 36 and,

rotating said string relative to said sealing means.

39. The method of claim 35, and

establishing fluid communication between said string and said borehole above the expanded sealing means;

circulating fluid through said drill string after said fluid communication is established; and

increasing the weight of said circulating fluid until said sealing means become contracted.

40. The method of claim 39 including:

raising said string to establish fluid communication between said borehole below said sealing means and the inside of said string, and

measuring the ambient pressure outside said string and below said expanded sealing means.

41. The method of claim 39. including,

lowering said string to close said first fluid communication.

* i i I i 

1. An elongated tool connectable to a string of liquid conducting hollow members for insertion into a wellbore, said tool comprising: a hollow outer mandrel; inflatable sealing means mounted on said outer mandrel; pressure control means mounted on said outer mandrel below said sealing means and being operatively coupled to said sealing means; said pressure control means a. having means for inflating said sealing means when the outside ambient pressure outside the tool in the wellbore becomes greater than the inside ambiEnt pressure inside the inner bore of the tool, b. having means for deflating said sealing means when said outside ambient pressure below said sealing means becomes less than said inside ambient pressure, and c. being operable solely in response to changes in the pressure difference between said outside and inside pressures; a hollow inner mandrel extending through said outer mandrel, said inner mandrel being connectable between said hollow members, each end of said outer mandrel being sealingly and slidably mounted on said inner mandrel to allow said inner mandrel to be movable relative to said outer mandrel, and said inner mandrel defining an upper port for establishing fluid communication between the inner bore of said inner mandrel and the inner bore of said outer mandrel.
 2. The tool of claim 1 including, disabling means coupled to said pressure control means to disable said control means when said tool is initially inserted into said wellbore, and said disabling means changing to enabling means when said inside ambient pressure becomes greater than said outside ambient pressure.
 3. The tool of claim 1 including, normally closed, first fluid communication means mounted on said outer mandrel above said sealing means, and said communication means open to establish fluid communication between the inside and outside of said tool above said sealing means after said sealing means have effectively sealed off the wellbore around said tool, and the pressure below said sealing means becomes greater than the pressure above said sealing means, and said inside ambient pressure remains less than said outside ambient pressure below said sealing means.
 4. The tool of claim 3 including, second fluid communication means in said outer mandrel for maintaining fluid communication between said inner mandrel and said pressure control means.
 5. The tool of claim 4 wherein said first fluid communication means is closed when said second communication means is and vice versa.
 6. The tool of claim 5 wherein said second fluid communication means is open when said sealing means is inflated thereby allowing an increase in the pressure inside said inner mandrel to operate on said control means to thereby deflate said sealing means.
 7. The tool of claim 6 wherein said upper port is in fluid communication with said second communication means when said inner mandrel is moved to an elevated position relative to said outer mandrel.
 8. The tool of claim 7 wherein said upper port is in direct fluid communication with said first communication means when said inner mandrel is positioned below said elevated position by a first predetermined distance.
 9. The tool of claim 5 wherein said first communication means includes a circulating valve having a body portion coupled to said sealing means.
 10. The tool of claim 9 wherein said second fluid communication means includes an operating valve having a body portion coupled to the body portion of said circulating valve to allow the body portions of said circulating and operating valves to move in unison.
 11. The tool of claim 10 wherein said second fluid communication means defines an elongated second chamber between said inner and outer mandrels for conducting fluid from said inner mandrel through said upper port and said second communication means to said first sensing element.
 12. The tool of claim 11 wherein said second chamber fluidly communicates with said first fluid communication means to allow fluid circulation between the inside and outside of said tool subsequent to the establishment of an effective seal by said sealing means against the wall of said wall bore.
 13. The tool of claim 12 including intermediate seal means between said inner and outer mandrels adapted to seal off said upper port from said second chamber dependent upon the relative longitudinal positions of said mandrels.
 14. The tool of claim 13 wherein said seal means include a top end seal and a Bottom end seal to seal off said second chamber.
 15. The tool of claim 9 wherein the first communication means includes a second differential-pressure sensing element movably mounted on said outer mandrel, and said second sensing element assisting in maintaining said circulating valve closed when the pressure inside said inner mandrel is greater than the ambient outside pressure above said sealing means.
 16. The tool of claim 15 wherein said second sensing element is a piston movably mounted on said outer mandrel.
 17. The tool of claim 1 including, releasable securing means for coupling said inner mandrel to said outer mandrel, said securing means being released by said pressure difference, and said inner mandrel being longitudinally movable relative to said outer mandrel only after said sealing means, in use, seals off said wellbore.
 18. The tool of claim 17 including, normally closed third fluid communication means mounted on said inner mandrel below said sealing means for establishing fluid communication between said inner mandrel and said borehole and, said third communication means opening upon the upward movement of said inner mandrel relative to said outer mandrel by a second predetermined longitudinal distance.
 19. The tool of claim 18 wherein the movement of said inner mandrel relative to said outer mandrel by an amount less than said second predetermined distance allows said third communication means to remain closed, said second communication means to remain closed, said first communication means to remain open, said upper port to be in direct communication with said second communication means, and said second communication means to be sealed off from said first communication means whereby a suitable substance can be circulated downwardly through said inner mandrel to shut in said wellbore.
 20. The tool of claim 18 wherein said third communication means includes a pressure-sampling valve having a body portion fixedly secured to said inner mandrel, and said inner mandrel defines a bottom port for maintaining direct fluid communication with said third communication means.
 21. The tool of claim 20 wherein said third communication means includes a third differential-pressure sensing element, said third sensing element assisting in maintaining said pressure sampling valve closed when the pressure inside said inner mandrel is greater than the ambient outside pressure below said sealing means, and said inner mandrel defines an intermediate port fluidly communicating with said third sensing element.
 22. The tool of claim 21 wherein said third communication means include a spring for biasing said third sensing element in a direction to assist in maintaining said pressure-sampling valve closed.
 23. The tool of claim 1 including, a normally closed third communication means between said inner mandrel and the outside of said tool below the sealing means, operating means mounted on the upper end of said inner mandrel to mechanically close said first communication means while opening said third communication means, whereby an increase in pressure inside said inner mandrel will cause said pressure control means to be isolated thereby to prevent the deflating of said sealing means.
 24. The tool of claim 23 wherein said operating means is a top connector for connecting said inner mandrel to a top hollow member.
 25. The tool of claim 1 wherein said sealing means define a first chamber; a liquid filling said chamber; and said control means controlling the pressure of the liquid in said first chamber.
 26. The tool of claim 25 wherein said control means include: a first differential-pressure sensing element responsive to said pressure difference, and a mechanism controlled by said first sensing element.
 27. The tool of claim 25 wherein said sealing means includes an inflatable element adapted to seal off said wellbore when said first chamber becomes pressurized.
 28. The tooL of claim 26 wherein said first sensing element is a piston mounted on said outer mandrel for longitudinal movement.
 29. The tool of claim 28 wherein said mechanism includes a piston adapted to move in said first chamber.
 30. The tool of claim 28 including, locking means for initially securing said mechanism to said outer mandrel, and said locking means releasing said mechanism when the pressure inside said inner mandrel becomes greater than the outside ambient pressure.
 31. The tool of claim 30 wherein the movement of said first sensing element exerts a downward force against said locking means to release said locking means.
 32. The tool of claim 31 wherein said inner mandrel, subsequent to the release of said locking means and the establishment of an effective seal in said wellbore by said sealing means, is free to reciprocate and rotate relative to said outer mandrel.
 33. The tool of claim 32 including a check valve positioned near the bottom end of said inner mandrel to prevent fluid from the wellbore from entering into said inner mandrel.
 34. A hollow well tool connectable to a string of hollow members for circulating fluid between said string and an opening, said tool comprising: a packer which, in normal use, is contracted to allow unrestricted fluid circulation between said string and said opening, said packer being susceptible of radial expansion to seal off said opening, said packer having a resilient member with an outer surface which, in use, engages the wall of said opening and forms a sealing surface therewith, pressure responsive control means coupled to said packer, said control means, in normal use, being deactivated and becoming activated when the outside ambient pressure becomes relatively high, said control means, when activated, enabling said packer to radially expand, an outer hollow mandrel operatively supporting said packer and said pressure responsive means, and a hollow inner mandrel carrying said outer mandrel, said inner mandrel, in use, being connectable between said tubular members and being susceptible of longitudinal movement or rotation relative to said outer mandrel.
 35. A method for controlling a well having a borehole filled with a fluid including: lowering a string of hollow members into said borehole, one of said hollow members comprising a detachable and expandable sealing means; continuously monitoring the outside ambient pressure outside said sealing means relative to the inside pressure inside said string; using a predetermined value of the pressure difference between the outside and inside pressures to cause said sealing means to radially expand; detaching said sealing means from said one hollow member; and moving said string relative to said sealing means.
 36. The method of claim 35 and, using another value of said pressure difference to cause said sealing means to contract.
 37. The method of claim 36 and, reciprocating said string relative to said sealing means.
 38. The method of claim 36 and, rotating said string relative to said sealing means.
 39. The method of claim 35, and establishing fluid communication between said string and said borehole above the expanded sealing means; circulating fluid through said drill string after said fluid communication is established; and increasing the weight of said circulating fluid until said sealing means become contracted.
 40. The method of claim 39 including: raising said string to establish fluid communication between said borehole below said sealing means and the inside of said string, and measuring the ambient pressure outside said string and below said expanded sealing means.
 41. The method of claim 39 including, lowering said string to close said first fluid communication. 